How Can You Use United Miles to Upgrade Seats?
If you have made reservations with United upgrade with miles and would like to upgrade your seat, then you have the following three ways available to request an Upgrade for your reservation made with United airlines.
Through the MileagePlus account.
Travellers may request upgrades using your MileagePlus account. Passengers are required to visit the official website of United airlines. Once there, passengers are required to make sure that they have an existing reservation with the airline to get upgrades.